\begin{table}%t4
\caption{\label{5:tab:coprop}Results from molecular line radiative transfer modelling.}
\par
%\centerline
{\small
\begin{tabular}{l l l l l l}
\hline \hline
Line & \multicolumn{2}{c}{Model 1$^a$} &\multicolumn{2}{c}{Model 2$^a$} & Obs.\\ 
 & $\int T_{\rm{MB}}$ & $T_{\rm{peak}}$$^b$ & $\int T_{\rm{MB}}$ & $T_{\rm{peak}}$$^b$ & $T_{\rm{peak}}$  \\ 
 \hline
CO 2--1 & 9.4 & 5.0/22.2 & 10.4 & 4.5/78.9 & 22.4\\
CO 3--2 & 8.0 & 4.7/22.5 & 7.1  & 3.8/55.8 & 19.4\\
CO 4--3 & 7.3 & 4.2/16.9 & 4.7  & 3.1/47.3 & 14.9\\
CO 6--5 & 6.8 & 3.4/4.8 & 5.1  & 2.7/5.2 & 9.5\\
CO 7--6 & 4.1 & 2.2 & 4.0 & 2.2  & 8.6\\
$^{13}$CO 3--2 & 4.6 & 3.7/3.8 & 5.9 & 3.6/10.7 & 11.4\\
$^{13}$CO 4--3 & 3.5 & 2.8 & 4.2 & 2.6/3.8 & 5.5\\
$^{13}$CO 6--5 & 1.9 & 1.2 & 1.9 & 1.2 & 2.9\\
$^{13}$CO 8--7 & 0.8 & 0.5 & 0.8 & 0.5 &$<$0.9\\
C$^{18}$O 3--2 & 1.3 & 1.2 & 3.5 & 2.9 & 3.3\\
C$^{18}$O 6--5 & 1.0 & 0.7 & 1.0 & 0.7 & $<$0.5\\ \hline
HCO$^+$$^c$ 4--3 & 3.5 & 2.3/11.8 & 2.8 & 2.5/8.3 & 5.4\\ 
H$^{13}$CO$^+$ 4--3 & 0.75 & 0.7 & 0.75 & 0.7 & 1.0\\ \hline
\end{tabular}}
\par
\medskip
$^a$~Model 1 has a jump abundance profile with $X_0$/$X_{\rm d}$ of
$2.7\times10^{-4}/1\times10^{-5}$. Model~2 has a drop abundance
profile with $X_0/X_{\rm d}/X_0$ of
$2.7\times 10^{-4}/1\times10^{-5}/2.7\times10^{-4}$.\\ 
$^b$~For some lines, the peak temperature is given as X/Y. The first value is
the actual $T_{\rm{peak}}$ in the model profile. The second value
refers to the peak of a Gaussian fitted to the line wings of model
profiles which show self-absorption.  If only a single number is
given, the modelled line is Gaussian in nature and does not have
self-absorption. \\
$^c$~HCO$^+$ abundances of $X_0$ and $X_{\rm d}$ are $2.0\times 10^{-8}$ and $3.0\times 10^{-9}$. 
\end{table}